This invention relates to an improved cartridge for containing and dispensing viscous material such as caulking compound. These cartridges are in widespread use and quite familiar to the average homeowner, who at one time or another must seal or weather-proof a surface in his home.
Generally, the cartridges are comprised of a cylindrical tube having at one end a fixed circular wall. This fixed wall has a discharge opening which is covered by a frangible seal to prevent leakage of the material contained in the tube, and also to prevent the material from being exposed to air before the cartridge is used. A spout or nozzle is attached to the fixed end wall for easy application of the caulking. The other end of the tube is usually closed by a flat circular piston slidably mounted in the tube.
Cartridges are usually used in combination with a dispensing gun having a plunger by which pressure is applied to the material in the tube. The plunger presses against the slidable piston of the tube pushing it through the tube thereby causing the material to discharge.
One shortcoming that has been associated with known dispensing cartridges is the undesirable discharge of material that continues even after the plunger has been withdrawn. This excess discharge is generally caused by pressures built up in the viscous material when the plunger applies a force to it.
Several methods have been devised to cope with this shortcoming. One method employs a cartridge having a shut off nozzle. This cartridge has a fixed end wall and a closure disc carried by the nozzle. Each have a discharge opening formed therein. By rotating the nozzle relative to the fixed end wall the openings are brought into alignment to allow discharge of material. To stop the flow of material the nozzle is rotated so that the discharge openings are not aligned.
Another known cartridge employs valves to control the discharge of material. Depending on whether the valves are open or closed the material in the cartridge may or may not be discharged.
With the above two devices manipulation by means of rotating a nozzle or closing valves is required to stop the flow of material. Though this extra manipulation is only a minor inconvenience it would be preferable for a cartridge to be able to stop the flow of material by merely pulling back the plunger. In addition, it would be preferable to keep the cartridge, as well as the dispensing gun, as simple in construction as possible, having fewer parts that may malfunction or increase the cost of the cartridge.
One device that attempts to accomplish this is a cartridge that uses a flexible member of semi-spherical configuration instead of a flat piston. In operation the plunger of the gun presses against the semi-spherical member thereby flattening the member. Application of additional pressure forces the member through the tube causing the material therein to be discharged. Theoretically when the plunger is released the forces in the tube act in the direction of the spherical member to restore it to its original configuration, rather than in the opposite direction to force material out of the tube. In practice, however, this device has been found not to be a fool-proof method of preventing unwanted discharge because only a small area of the semi-spherical member is displaced by the pressure of the plunger. Accordingly, only a portion of the energy accumulated in the material is dissipated in restoring the semi-spherical member to its original configuration. In addition, because the semi-spherical member is in tight contact with the inner surface of the cartridge at all times, it is easier for the forces in the viscous material to act to discharge the material than it is to move the semi-spherical member back. As a result the remaining energy causes leakage of the material from the cartridge.
It is an object of the invention to overcome the shortcomings of the prior art and to provide a cartridge for containing and dispensing viscous material which is simple in construction and in which the viscous material will substantially stop flowing when the plunger is pulled, and which does not require rotation or manipulation of additional parts.
It is a further object of this invention to provide a cartridge for containing and dispensing viscous material which is inexpensive to manufacture and simple to operate.